Key and key-seat



(ModeL) I E. EINFELDT;

' KEY AND KEY SEAT. No. 319,078. PatentedJune 2, 1885.

there drains Parent Garret.

EMIL EINFELDT, OF DAVENPORT, IOW A.

KEY ANDKEY=SEAT.-

$PBC'IPICATION forming part of Letters Patent No. 319,078, dated June 2, 1885.

I Application filed April 10, 1885. (Model) T0 aZZ whom it may concern: b

Be it known that I, EMIL EINFELDT, of Davenport, in the county of Scott and State of Iowa, have invented certain new and useful Improvements in Keys and Key- Seats, of which the following is a specification.

My invention consists in a novel form of key-seat and key for securing wheels, cranks, hubs, &c., to shafts.

Figure 1 is an end view of a shaft showing a crank secured thereon by means of my improved key. Fig. 2 is a perspective view of the shaft and key; Fig. 3, face and edge views of the key; Figs. 4 and 5, diagrams illustrating certain matters hereinafter referred to.

Prior to my invention keys have been made in a variety of forms, of which the more common are a wedge of rectangular cross-section and a tapered one of circular form in crosssection. Rectangular keys weaken the shaft, and do not fill the seat from side to side with such accuracyas is required to properly secure the crank or hub upon the shaft, and round pins are unsatisfactory, because if made of sufficient diameter to afford the requisite strength and proper bearing-face a seat of undue size is required, as will be hereinafter more fully explained. By my improved key I avoid these difficulties and secure a key-seat that is much easier to cut in the shaft than the ordinary rectangular seat.

A indicates a shaft; B, the key-seat formed therein; 0, a crank-arm, and D the key constructed in accordance with my invention.

The keyseat is of concave form, being curved on the arc of a circle having its center at or near the upper line of the key in Fig. 1. This seat may be made shallower at one end than at the other, in order that the key may be driven firmly to place and caused to bind or wedge therein. The key D is of ordinary form, except that its inner face, or that face which is turned toward the axis of the shaft A, is made convex, being curved on the arc of a circle concentric with that on which the key-seat is struck. The usual taper or wedge form is preserved from end to end in a direction radial to the axis of the shaft; hence the inclination of the bottom of the seat is not important. The upper side of the key is rectangular and the seat in the crank or other attached body is of like form.

The key-seat and key being thus formed, the crank, wheel, hub, or other body, 0, is applied to the shaft and the key is driven in, as usual; but owing to the form of the keyseat and the key the latter bears not only at the bottom of the seat, but equally at all points therein, completely and closely filling the seat and leaving no possible space for play of the parts.

Owing to the convex portion of the key within the seat, a large surface and ample width of metal are secured. It will also be observed that if the slightest space or play should by accident be left between the key and its seat the curved faces riding one upon the other would cause the key to wedge between the parts and lock them firmly together. The difference between this and the ordinary rectangular key is very marked. lVith the rectangular key an angle is necessarily formed at each side of the key-seat, as indicated in the diagram Fig. 4, from which angle a break will much more readily begin than from a curved face presenting no angle. Again, the sides or walls of the seat being upright, the pressure is directly against one or the other of said walls, and the greatest resistance is indicated by the dotted lines in Fig. 4:. With the curved face shown in Fig. 1, however, no

angle is produced, a greater body of metal is.

interposed between the bearingface of the key and the periphery of the shaft, and the resistance is distributed over the shaft in lines radial t0 the center from which the curved face of the key is struck; hence with only a very shallow key-seat there is no possibility of the walls of said seat being broken out, and the shaft is not weakened as it is by a deeper key-seat. By making only the lower face of the key of the form described and shown, and the upper face flat or approximately so, a thin or shallow key is produced, so that it is not necessary to cut a large seat for it in the hub, crank, or other body, as would be the case if a circular pin were employed with a curved face of like radius and similarly seated in the shaft. This distinction is plainly illustrated by the larger dotted circle in Fig. 5.

-If a circular pin having a diameter only equal to the thickness of the key be used, as indicated by the smaller circle, Fig. 5, the cross-section presented at the circumference of the shaft will be insufficient to resist the strain put upon it.

The precise curvature of the face of thekey is not essential, but may be varied considerably, though I prefer to make it an arc of a circle, for convenience, and to secure a uniform distribution of strains.

Having thus described my invention, What I claim is 1. A key for securing wheels, cranks, 850., to shafts, having a fiat body and a convex face on. one side, substantially and for the purpose set forth.

2. In cornbinationwith shaft A, having con- 

